The development and inhibition of physical aggression in early childhood : measurement and associations

Research suggests that the age at which humans are most physically aggressive is at the end of the second year of life. Typically, children will subsequently show a gradual decline in aggression during the third year of life and by the time they reach kindergarten, they will have learned to inhibit much of their aggressive tendencies (Arsenio, 2004a; Cote et al., 2007; Cote et al., 2006; Gauthier, 2003; Tremblay, 2000; Tremblay, 2001). Tremblay (2001) has discussed the possibility of a sensitive period (from approximately 24-36 months of age) for learning to restrain physical aggression. Two studies were conducted to assess the relative and cumulative associations between physically aggressive behaviour and both cognitive (executive function and vocabulary skills) and social-interactional (attachment and parenting styles) factors at different developmental periods. The first study involved parents and teachers reporting on a total of 436 children with a mean age of 42 months. The second study involved parents and teachers reporting on 85 children with a mean age of 34 months. Each of the studies were short-term longitudinal in nature involving a second wave of data collection to track the connections between changes in cognitive and/or social interactional functioning and changes in physically aggressive behavior over a one-year period. Results of this research suggest that aspects of executive function (inhibition and emotional control especially) appear to be particularly important in the prediction of physical aggression in this age period. Accordingly, support was obtained for Moffitt’s (1993) theory emphasizing the role of cognitive processes in contributing to the development of early aggressive behavior. Implications for these findings are discussed with consideration of the plausibility of a sensitive period